1. Field of the Invention
This invention relates to mandrels for holding tubular workpieces during machine tool cutting operations performed on the end areas of the workpieces.
2. Description of Prior Art
This invention relates to an improved mandrel construction intended to permit precise beveling, circumferential cutting, scoring, or other similar operations on the end areas of tubular workpieces in planes that are inclined relative to a plane that is perpendicular to the centerline axis of the workpiece. Stated differently, the mandrel of the present invention enables angular adjustment between the cutting axis of the machine tool and the centerline axis of the tubular workpiece.
Prior art mandrels used heretofore are generally arranged to precisely hold a tubular workpiece so that its centerline axis coincides with the cutting axis of the machine tool used to perform a cutting operation on the end area of the workpiece, or circumferentially about the outer surface of the workpiece. Provisions are not usually made in the prior art to transversely pivot the mandrel or the workpiece relative to the cutting axis of the machine tool, since to do so would introduce inaccuracies in the cutting operation unless the mandrel was specifically designed for precise pivotal motion while maintaining tool accuracy and cutting performance. This has been so, even though it has been recognized that it would be highly desirable to perform a beveling or other cutting operation on the end of a tubular workpiece in a plane that is inclined relative to the plane that is perpendicular to the centerline axis of the workpiece. For convenience, such a cutting procedure is referred to as a "miter cut".
The mandrel according to the present invention is intended to enable such "miter" cuts to be made on tubular workpieces, generally in preparation for a welding operation involving the end area of the workpiece. Such cuts are made by tools called pipe or tube "end prep" tools, which is a short expression for "end preparation" tools. Tools of this type are conventional, and typical examples of a beveling tool can be observed, with a specific mandrel configuration, in U.S. Pat. No. 3,229,555. A typical example of a tube cut-off tool can be seen in U.S. Pat. Nos. 587,093, 1,115,277 and 1,985,541. Still another example of a tube end "milling" tool can be seen in U.S. Pat. No. 1,972,022, which also features a typical, non-adjustable angle mandrel arrangement.
While mandrels used in such applications are typically "fixed" against angular or pivotal motion, it has nevertheless been recognized in the field that it would be highly desirable to support a workpiece at an angle relative to the cutting axis of the tool so that "miter" cuts can be made to allow for slight angular differences between tubular workpieces being welded together end-to-end. The present invention is intended to provide such a mandrel that permits miter cuts to be made on tubular workpieces while preserving total overall performance and accuracy of the cutting operation.